Opinion on best client interface

[mottwsc]

I'm developing an internet-based entertainment application using php and mySQL for teens and young adults. Not video games with graphics or anything like that, but closer to a social network. Right now, I generate HTML using php. I'm trying to decide on a client interface based on (a) how it looks/behaves (Web 2.0 vs. other), (b) how easy it is to maintain, and (c) the compatability with MSIE, Firefox and maybe other browsers. The choices for the client interface are:
(1) the current HTML (some larger icons included with text)
(2) HTML, plus some Javascript for menu interactivity/non-repainting of screens
(3) HTML with IFrames (not sure if these are desirable given potential hacking risk)
(4) Flash (nice interactivity but a lot of overhead to create/update - unless there is a RAD tool for Flash)
(5) not sure I want to go the AJAX route at this point, probably not necessary

I'd appreciate any experienced person's advice on this. Thanks!

[Horus_Kol]

Ajax is not scary... it is actually quite simple, especially if using a library which does all the request/response handling for you (there's a few, but I prefer prototype (www.prototypejs.org) - because of other features in the library).

Flash - meh... I prefer menus to not take long to load...
Plus - search engine spiders cannot follow links in a Flash menu.

IFrames - old school... use server scripts or just SSI to deal with common content.

So - HTML and JavaScript...
Go wild :) just make sure that your navigation works without JS as well as with it (same with accessing content when using Ajax) - that's part of a philosophy known as progressive enhancement